fix(nxp-ddr): add checking return value

Coverity Issue 21268351
Fixed unused value of xspi read while reading training values from
xspi during warm reset.

Signed-off-by: Maninder Singh <maninder.singh_1@nxp.com>
Signed-off-by: Jiafei Pan <Jiafei.Pan@nxp.com>
Change-Id: I779587afedb1c73d174a132bbfbcb21bf45bdff8
1 file changed